Organochlorine contaminants in endangered Hawaiian monk seals from four subpopulations in the Northwestern Hawaiian Islands

Monk seals (Monachus monachus) in the Mediterranean Sea: The threat of organochlorine contaminants and polycyclic aromatic hydrocarbons

The Mediterranean monk seal (Monachus monachus) is an emblematic species of conservation concern. Anthropogenic pressures have led to severe population declines and significant fragmentation of the remaining populations. Because of their close relationship with coastal areas, Mediterranean monk seals may be potentially exposed to pollution from agricultural sources, as well as from oil tanker spills. Although monitoring of pollution has long been considered a priority for this species, data on monk seal contamination levels are scarce. In this study, 55 blubber samples of all genders and age classes collected during necropsies (1995-2013) from seals of the Eastern Mediterranean subpopulation were analyzed for organochlorine compounds (OCs), i.e., hexachlorobenzene (HCB), polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDTs), and polycyclic aromatic hydrocarbons (PAHs). Overall, PCBs > DDTs ≫ PAHs > HCB in all samples. Results showed a significant downward trend over the 19-year period for DDTs and HCB. No marked pattern was found for PAHs, even though relative abundance of cancerogenic PAH fraction rose in recent years. PCB levels in subadult specimens increased noticeably over time despite worldwide ban. Our findings did not suggest recent releases of DDT or new pesticides (e.g., Dicofol) in the environment, but may indicate an improper disposal of ancient storages of PCBs or a remobilization from reservoirs. OC levels exceeded thresholds that are commonly associated with immunosuppression and reproductive impairment in other pinnipeds. Hence, OCs could be responsible of potential toxicological effects in this subpopulation. This study represents the first report on PAH and one of the few reports on OC bioaccumulation in Mediterranean monk seals. Based on the levels found in the blubber of monk seals from the Eastern Mediterranean, and given the known harmful effects associated to the prolonged exposure to these substances and the reduced long-term expectations of species recovery, regular monitoring is advocated.

Trophic and spatial patterns of contaminants in fishes from the Republic of the Marshall Islands in the equatorial Pacific

The Republic of the Marshall Islands (RMI) has been affected by marine pollution from militarization and urbanization. To address concerns raised by the Marshall Islands Marine Resources Authority, this study examined concentrations of dissolved contaminants in reef and pelagic fishes in the RMI and assessed potential associated risks. Metals, organochlorine pesticides, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs) were examined in reef and pelagic fishes from six atolls: Kwajalein, Majuro, Jaluit, Utirik, Rongelap, and Wotje. Clear trophic patterns emerged for metals. Total arsenic was highest in higher trophic level reef fishes, particularly in the camouflage grouper (Epinephelus polyphekadion) (>100 μg g^-1 total As), but inorganic arsenic was negligible in higher trophic levels and showed an inverse trend with the highest percentages present in parrotfishes and herbivores. Copper and mercury were elevated in higher trophic level reef and pelagic fishes, respectively, and the maximum mercury concentrations (6.45 μg g^-1 in Gymnosarda unicolor) were among the highest reported in the Pacific. Conversely, cadmium and lead were highest in lower trophic levels, like surgeonfishes and parrotfishes. PCBs were more clearly linked to locations and were highest at two atolls with military history (Kwajalein and Jaluit) (>U.S. EPA Screening Value of 2.5 ppb). PAHs were ubiquitous across taxa (detected in 97% of samples), but the highest concentrations were in lower trophic levels. Organochlorine pesticides were detected at very low concentrations that do not likely pose a risk. We compare concentrations to established thresholds for human health and find that - for specific locations and species - contaminant concentrations may pose a risk to fish and other marine taxa, as well as human consumers. This study provides baseline information that aids the development of marine conservation and public health recommendations and addresses a data gap that persists for marine pollution throughout the Pacific Islands.

Persistence, bioaccumulation and vertical transfer of pollutants in long-finned pilot whales stranded in Chilean Patagonia

Long-finned pilot whales (LFPW) are cetaceans with strong social groups often involved in mass strandings worldwide. However, these beachings occur for reasons that are not fully understood. In 2016, 124 LFPW were stranded on the Chilean Patagonian islands, offering a unique opportunity to obtain crucial information on the ecology, biology, and genetics of this population. In addition, we examined whether persistent organic pollutants (POPs) and trace elements (TEs) were responsible for this mass mortality. Stable isotopes (δ¹³C & δ¹⁵N) and genetic analyses were used to reconstruct the trophic ecology, social structure, and kinship of LFPW and compared to POPs and TEs levels found in LFPW. Mitochondrial DNA analyses on 71 individuals identified four maternal lineages within the stranded LFPW. Of these animals, 32 individuals were analyzed for a suite of POPs, TEs, and lipid content in blubber. The highest levels were found for ΣDDXs (6 isomers) (542.46 ± 433.46 ng/g, lw) and for total Hg (2.79 ± 1.91 mg/kg, dw). However, concentrations found in these LFPW were lower than toxicity thresholds and those reported for LFPW stranded in other regions. Evidence was found of ΣDDX, Σ7PCBs, and Cd bioaccumulation and maternal transfer of POPs in mother/offspring groups. Nevertheless, no clear relationship between contaminant concentrations and LFPW mortality was established. Further research is still needed to assess LFPW populations including conservations status and exposure to chemicals in remote areas such as Patagonia.

Bioaccumulation and human health risk assessment of DDT and its metabolites (DDTs) in yellowfin tuna (Thunnus albacares) and their prey from the South China Sea

DDTs were detected in yellowfin tuna (Thunnus albacares, 92.1-221.8 ng‧g^-1 lipid weight) and their prey (54.9-93.5 ng‧g^-1 lipid weight) from the South China Sea (SCS). DDT levels reported in this study were lower than those of the previous studies indicated the recent mitigation of DDT contamination in the SCS. Higher DDT levels were observed in fat abdominal muscle than lean dorsal muscle in adult yellowfin tuna. Meanwhile, DDT levels in adult yellowfin tuna were higher than the young ones. The composition profiles of DDT and its metabolites suggested DDTs in fish in the SCS were mainly derived from the historical use of technical DDTs. DDTs were biomagnified through food chains with the trophic magnification factor of 2.5. Risk assessment results indicated that dietary exposure to DDTs through lifetime fish consumption from the SCS would pose little cancer and noncarcinogenic risk to coastal residents.

Persistent organic pollutants in killer whales (Orcinus orca) of the Russian Far East

Exposure to persistent organic pollutants (POPs) is a key factor in predicting the collapse of global killer whale (Orcinus orca) populations due to reproductive and immune impacts. Blubber biopsies from killer whales (n = 25) were collected in the Russian Far East in 2002-2004. Biopsies were analyzed for ΣDDT, ΣPCB, and HCB concentrations. A subset of biopsies was further examined for additional contaminants, ΣPBDE, ΣHCH, ΣCHLD, mirex, and dieldrin. Mean concentrations were compared across resident (fish-eating) and transient (mammal-eating) ecotypes and between sexes. ΣPCB analytes (resident males 18,000, resident females 1200, and transient males 420,000 ng g^-1 lw) and HCB (resident males 750, resident females 81, and transient males 6200 ng g^-1 lw) differed significantly (p < 0.001). No significant difference was observed between sexes. Notable disparities in contaminant levels between ecotypes support the major toxicological theories of contaminant bioaccumulation and dietary impacts on individual contaminant load.

Tropical seabirds sample broadscale patterns of marine contaminants

Contaminants in the marine environment are widespread, but ship-based sampling routines are much narrower. We evaluated the utility of seabirds, highly-mobile marine predators, as broad samplers of contaminants throughout three tropical ocean regions. Our aim was to fill a knowledge gap in the distributions of, and processes that contribute to, tropical marine contaminants; and explore how species-specific foraging ecologies could inform or bias our understanding of contaminant distributions. Mercury and persistent organic pollutant (POPs) concentrations were measured in adults of five seabird species from four colonies in the central Pacific (Laysan and Tern Islands, Hawaii; Palmyra Atoll) and the eastern Caribbean (Barbuda). Blood-based total mercury (THg) and 89 POPs were measured in two seabird families: surface-foraging frigatebirds (Fregata spp.) and plunge-diving boobies (Sula spp.). Overall, largescale contaminant differences between colonies were more informative of contaminant distributions than inter-specific foraging ecology. Model selection results indicated that proximity to human populations was the best predictor of THg and POPs. Regional differences in contaminants were distinct: Barbudan Magnificent Frigatebirds had more compounds (n=52/89 POP detected) and higher concentrations (geometric mean THg=0.97μgg^-1; mean ΣPOP₅₃=26.6ngmL^-1) than the remote colonies (34-42/89 POP detected; range of THg geometric means=0.33-0.93μgg^-1; range of mean ΣPOP₅₃:7.3-17.0ngmL^-1) and had the most recently-synthesized POPs. Moderate differences in foraging ecologies were somewhat informative of inter-specific differences in contaminant types and concentrations between nearshore and offshore foragers. Across species, contaminant concentrations were higher in frigatebirds (THg=0.87μgg^-1; ΣPOP₅₃=17.5ngmL^-1) compared to boobies (THg=0.48μgg^-1; ΣPOP₅₃=9.8). Ocean currents and contaminants' physiochemical properties provided additional insight into the scales of spatial and temporal contaminant exposure. Seabirds are excellent, broad samplers with which we can understand contaminant distributions in the marine environment. This is especially important for tropical remote regions that are under-sampled.

Survey for Placental Disease and Reproductive Pathogens in the Endangered Hawaiian Monk Seal ( Neomonachus schauinslandi)

There is considerable temporal and spatial variability in the reproductive rates of Hawaiian monk seals (HMS; Neomonachus schauinslandi). Poor reproductive performance limits the recovery of this endangered species; however, causal factors are not fully understood. There is serologic evidence that HMS are exposed to pathogens that can impact reproductive success, but the prevalence of placental infections in HMS has not been evaluated. Placental tissues ( n=50), including tissues from 25% of known HMS births, were opportunistically collected in 2011 from six Northwestern Hawaiian Islands and three main Hawaiian Islands. Reproductive histories of the sampled females were representative of the breeding population, as determined through comparisons in age of primiparity and mature reproductive rate. Placental tissues were examined histologically and screened by PCR for Coxiella burnetii, Brucella spp., Chlamydia spp., Leptospira spp., herpesviruses, and Toxoplasma gondii. There was no histologic evidence of placental pathology, and molecular analyses were negative. These negative results can be used to estimate pathogen prevalence in the nonsampled population. For an approximate population size of 1,300 HMS, we can estimate with 99% confidence that the prevalence of each pathogen tested is 9% or less. This is low relative to other pinnipeds and indicates that factors other than reproductive pathology, such as resource limitation, may drive variability in HMS reproductive rates. Further investigation into the cumulative impacts of resource limitation and other stressors on HMS reproduction is warranted.

Utility of fur as a biomarker for persistent organic pollutants in Australian fur seals (Arctocephalus pusillus doriferus)

Persistent Organic Pollutants (POPs) can cause toxic effects in many species which include endocrine dysfunction, immunotoxicity, developmental defects and neoplasia. Species dominating the upper trophic level are vulnerable to these effects due to bioaccumulation. In Bass Strait, the Australian fur seal (Arctocephalus pusillus doriferus) is an important top order predator and sentinel species for ecosystem health. An alopecia syndrome is seen at high prevalence in juvenile, female Australian fur seals at Lady Julia Percy Island, Victoria, Australia. Previous investigations suggest causality could be due to an endocrine-like toxicant. The alopecia syndrome has significance for thermoregulation and is a likely risk factor for mortality. Fur collected from case (alopecic) and control (unaffected) seals sampled at Lady Julia Percy Island were analysed for POPs. To investigate the utility of fur for monitoring POPs concentrations in pinnipeds, a comparison of POPs concentrations in the fur and blubber of Australian fur seals stranded along the Victorian coast was undertaken. The concentration of selected POPs including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenyls (dl-PCBs), polybrominated diphenyl ethers (PBDEs) and perfluorooctane sulfonate/perfluorooctanoic acid (PFOS/PFOA) were determined in fur using either High Resolution Gas Chromatography-Mass Spectrometry or Liquid Chromatography-Mass Spectrometry. Results indicate detectable, and in some individuals, elevated levels of dl-PCBs, PCDD/Fs and PBDEs in juvenile fur seals sampled on Lady Julia Percy Island, with significantly higher levels of dl-PCBs in case compared to control seals. Elevated levels of dl-PCBs and PCDD/Fs were found in blubber samples collected from stranded fur seals with significant correlations between blubber and fur concentrations seen, particularly for dl-PCBs. This study discusses the significance of POPs concentrations in relation to the causality of an alopecia syndrome in the Australian fur seal, and assesses the utility of fur as a non-invasive biomarker to monitor POPs exposure in this sentinel species.

Persistent organic pollutants in fat of three species of Pacific pelagic longline caught sea turtles: Accumulation in relation to ingested plastic marine debris

In addition to eating contaminated prey, sea turtles may be exposed to persistent organic pollutants (POPs) from ingesting plastic debris that has absorbed these chemicals. Given the limited knowledge about POPs in pelagic sea turtles and how plastic ingestion influences POP exposure, our objectives were to: 1) provide baseline contaminant levels of three species of pelagic Pacific sea turtles; and 2) assess trends of contaminant levels in relation to species, sex, length, body condition and capture location. In addition, we hypothesized that if ingesting plastic is a significant source of POP exposure, then the amount of ingested plastic may be correlated to POP concentrations accumulated in fat. To address our objectives we compared POP concentrations in fat samples to previously described amounts of ingested plastic from the same turtles. Fat samples from 25 Pacific pelagic sea turtles [2 loggerhead (Caretta caretta), 6 green (Chelonia mydas) and 17 olive ridley (Lepidochelys olivacea) turtles] were analyzed for 81 polychlorinated biphenyls (PCBs), 20 organochlorine pesticides, and 35 brominated flame-retardants. The olive ridley and loggerhead turtles had higher ΣDDTs (dichlorodiphenyltrichloroethane and metabolites) than ΣPCBs, at a ratio similar to biota measured in the South China Sea and southern California. Green turtles had a ratio close to 1:1. These pelagic turtles had lower POP levels than previously reported in nearshore turtles. POP concentrations were unrelated to the amounts of ingested plastic in olive ridleys, suggesting that their exposure to POPs is mainly through prey. In green turtles, concentrations of ΣPCBs were positively correlated with the number of plastic pieces ingested, but these findings were confounded by covariance with body condition index (BCI). Green turtles with a higher BCI had eaten more plastic and also had higher POPs. Taken together, our findings suggest that sea turtles accumulate most POPs through their prey rather than marine debris.

Trace Element Concentrations in Liver of 16 Species of Cetaceans Stranded on Pacific Islands from 1997 through 2013

The impacts of anthropogenic contaminants on marine ecosystems are a concern worldwide. Anthropogenic activities can enrich trace elements in marine biota to concentrations that may negatively impact organism health. Exposure to elevated concentrations of trace elements is considered a contributing factor in marine mammal population declines. Hawai'i is an increasingly important geographic location for global monitoring, yet trace element concentrations have not been quantified in Hawaiian cetaceans, and there is little trace element data for Pacific cetaceans. This study measured trace elements (Cr, Mn, Cu, Zn, As, Se, Sr, Cd, Sn, Hg, and Pb) in liver of 16 species of cetaceans that stranded on U.S. Pacific Islands from 1997 to 2013, using high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) (n = 31), and direct mercury analysis atomic absorption spectrometry (DMA-AAS) (n = 43). Concentration ranges (μg/g wet mass fraction) for non-essential trace elements, such as Cd (0.0031-58.93) and Hg (0.0062-1571.75) were much greater than essential trace elements, such as Mn (0.590-17.31) and Zn (14.72-245.38). Differences were found among age classes in Cu, Zn, Hg, and Se concentrations. The highest concentrations of Se, Cd, Sn, Hg, and Pb were found in one adult female false killer whale (Pseudorca crassidens) at concentrations that are known to affect health in marine mammals. The results of this study establish initial trace element concentration ranges for Pacific cetaceans in the Hawaiian Islands region, provide insights into contaminant exposure of these marine mammals, and contribute to a greater understanding of anthropogenic impacts in the Pacific Ocean.

Deep-ocean foraging northern elephant seals bioaccumulate persistent organic pollutants

As top predators in the northeast Pacific Ocean, northern elephant seals (Mirounga angustirostris) are vulnerable to bioaccumulation of persistent organic pollutants (POPs). Our study examined a suite of POPs in blubber (inner and outer) and blood (serum) of free-ranging northern elephant seals. For adult females (N=24), we satellite tracked and sampled the same seals before and after their approximately seven month long foraging trip. For males, we sampled different adults and sub-adults before (N=14) and after (N=15) the same foraging trip. For females, we calculated blubber burdens for all compounds. The highest POP concentrations in males and females were found for ∑DDTs and ∑PCBs. In blubber and serum, males had significantly greater concentrations than females for almost all compounds. For males and females, ∑DDT and ∑PBDEs were highly correlated in blubber and serum. While ∑PCBs were highly correlated with ∑DDTs and ∑PBDEs in blubber and serum for males, ∑PCBs showed weaker correlations with both compounds in females. As females gained mass while foraging, concentrations of nearly all POPs in inner and outer blubber significantly decreased; however, the absolute burden in blubber significantly increased, indicating ingestion of contaminants while foraging. Additionally, we identified three clusters of seal foraging behavior, based on geography, diving behavior, and stable carbon and nitrogen isotopes, which corresponded with differences in ∑DDTs, ∑PBDEs, MeO-BDE 47, as well as the ratio of ∑DDTs to ∑PCBs, indicating the potential for behavior to heighten or mitigate contaminant exposure. The greatest concentrations of ∑DDTs and ∑PBDEs were observed in the cluster that foraged closer to the coast and had blood samples more enriched in (13)C. Bioaccumulation of POPs by elephant seals supports mesopelagic food webs as a sink for POPs and highlights elephant seals as a potential sentinel of contamination in deep ocean food webs.

Using cytochrome P4501A1 expression in liver and blubber to understand effects of persistent organic pollutant exposure in stranded Pacific Island cetaceans

Elevated levels of persistent organic pollutants (POPs) have been reported in tropical Pacific Island cetaceans and their environment. In addition, recent health concerns in cetacean populations have warranted investigation into potential physiological effects from POP exposure for this region. Cytochrome P450 1A1 (CYP1A1) is a candidate for examining such effects. This well-studied biomarker of exposure and effect was examined in stranded cetacean liver using immunoblot (n = 39, 16 species) and blubber using immunohistochemistry (n = 23, 10 species). Paired tissue samples allowed for CYP1A1 comparisons not only between species but also within each individual animal to examine differences between tissue types. Liver CYP1A1 expression correlated positively and significantly with blubber concentrations of all POP categories (n = 39, p < 0.050) except octachlorostyrene and pentachlorobenzene (p > 0.100). Among Stenella species, liver CYP1A1 tissue expression was correlated negatively with the sum of all blubber layer endothelial cell CYP1A1 expression (n = 14, p = 0.049). Overall, elevated expression of liver CYP1A1 confirms its use as a biomarker of POP exposure to cetaceans stranded in the tropical Pacific basin.

Persistent organic pollutant concentrations in blubber of 16 species of cetaceans stranded in the Pacific Islands from 1997 through 2011

Persistent organic pollutants (POPs) are toxic man-made chemicals that bioaccumulate and biomagnify in food webs, making them a ubiquitous threat to the marine environment. Although many studies have determined concentrations of POPs in top predators, no studies have quantified POPs in stranded cetaceans within the last 30 years around the Hawaiian Islands. A suite of POPs was measured in the blubber of 16 cetacean species that stranded in the tropical Pacific, including Hawai'i from 1997 to 2011. The sample set includes odontocetes (n=39) and mysticetes (n=3). Median (range) contaminant concentrations in ng/g lipid for the most representative species category (delphinids excluding killer whales [n=27]) are: 9650 (44.4-99,100) for ∑DDTs, 6240 (40.8-50,200) for ∑PCBs, 1380 (6.73-9520) for ∑chlordanes, 1230 (13.4-5510) for ∑toxaphenes, 269 (1.99-10,100) for ∑PBDEs, 280 (2.14-4190) for mirex, 176 (5.43-857) for HCB, 48.1 (<5.42-566) for ∑HCHs, 33.9 (<2.42-990) for ∑HBCDs, 1.65 (<0.435-11.7) for octachlorostyrene and 1.49 (<2.07-13.1) for pentachlorobenzene. ∑PCB concentrations in these Pacific Island cetaceans approach and sometimes exceed proposed toxic threshold values. Backward stepwise multiple regressions indicated the influence of life history parameters on contaminant concentrations when performed with three independent variables (species category, year of stranding, and sex/age class). No temporal trends were noted (p>0.063), but sex/age class influences were evident with adult males exhibiting greater contaminant loads than adult females and juveniles for ∑DDT, ∑PCBs, ∑CHLs, and mirex (p≤0.036). POP concentrations were lower in mysticetes than odontocetes for many compound classes (p≤0.003). p,p'-DDE/∑DDTs ratios were greater than 0.6 for all species except humpback whales, suggesting exposure to an old DDT source. These POP levels are high enough to warrant concern and continued monitoring.

Persistent organic pollutants in the endangered Hawaiian monk seal (Monachus schauinslandi) from the main Hawaiian Islands

Little is known about levels or effects of persistent organic pollutants (POPs) in Hawaiian monk seals (HMS) from the main Hawaiian Islands (MHI) subpopulation. This study examined concentrations of a large suite of POPs in blubber and serum of juvenile and adult HMS from the MHI. Adult females have the lowest blubber levels of most POPs, whereas adult males have highest levels. POPs in serum were significantly different in adult males compared with adult females for chlordanes and summed dichlorodiphenyltrichloroethanes (DDTs). Lipid-normalized concentrations of chlordanes, DDTs, polychlorinated biphenyls, and mirex in paired blubber and serum samples were significantly correlated. Contaminant levels from the MHI were at similar or lower levels than those from remote Northwestern Hawaiian Island populations. Determining initial ranges of POPs is an important step towards assessing one of the many potential health threats to this critically endangered species.

DDT in endangered Galapagos sea lions (Zalophus wollebaeki)

We characterize for the first time the presence of DDT and its metabolites in tropical Galapagos sea lions (Zalophus wolleabeki). ∑DDT concentrations in Galapagos sea lion pups sampled in 2005 and 2008 ranged from 16 to 3070 μg/kg lipid. Concentrations of ∑DDT in pups in 2008 averaged 525 μg/kg lipid and were 1.9 times higher than that (281 μg/kg lipid) detected in pups in 2005. These concentrations are lower than those reported in many pinnipeds elsewhere, comparable to those in Hawaiian monk seals, and higher than those in southern elephant seals. The health risk characterization showed that 1% of the male pups exceeded the p,p'-DDE toxic effect concentration associated with anti-androgenic effects reported in rats. The findings provide preliminary guidance on the relationship between DDT use and ecological impacts, serving as a reference point against which possible future impact of tropical DDT use can be assessed.

Contamination profiles of selected PCB congeners, chlorinated pesticides, PCDD/Fs in Antarctic fur seal pups and penguin eggs

The aim of this study was to investigate levels of some major environmental contaminants, such as polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and organochlorine pesticides in Antarctic samples. Concentrations of some persistent organic pollutants (POPs) were investigated in Antarctic fur seal pups and eggs of three species of penguins. Dichloro-diphenyl-trichloroethane (DDT) was the main pollutant, followed by PCBs; other organochlorine compounds such as hexachlorobenzene (HCB) and PCDD/Fs were usually found only in minor quantities. Adélie penguin eggs had significantly higher mean PCB concentrations (p<0.05) compared to the other two penguin species, but there was no difference in DDT levels (p>0.05). TEQ values in fur seal blubber in our study were one order of magnitude lower than those considered to elicit physiological effects in aquatic mammals. In general, POP concentrations in our samples suggested that likely the study populations were not currently at risk for adverse health effects, but indicated a clear need for further monitoring to assess the presence and time trend of a broad range of contaminants, mainly emerging POPs thought to be increasing in polar regions.